Anatomía del pecíolo de 16 especies de Polypodiaceae presentes en México

Background and aims: Several works have shown that the petiole possesses useful anatomical characteristics for differentiating groups. Therefore, we carried out a descriptive and comparative anatomical study of the basal, middle, and apical regions of the petiole of 16 species belonging to 8 genera of Polypodioideae growing in Mexico, to identify anatomical characters that can contribute to their delimitation and identification M&M: Samples were collected from the basal, middle, and apical regions of the petiole and processed according to the paraffin embedding technique to obtain permanent preparations. The generated information was evaluated through a clustering analysis and a principal component analysis. Results: All petioles showed an unistratified epidermis, a cortex differentiated into external and internal, and vascular bundles with Polypodium-type distribution. Differences were registered in the petiole diameter, indument type, circumendodermal band, and number of vascular bundles. Four types of external cortex are recognized and the presence of nectaries in Campyloneurum amphostenon and C. costatum is reported for the first time, as well as the glandular hairs inserted at the base of the scales in Microgramma percussa. Identification keys were elaborated. Conclusions: The anatomical characteristics of the petiole allow us to differentiate taxonomically the genera and most of the species analyzed, the most important traits being the petiole diameter, the characteristics of the circumendodermal band, and the presence of aerophores and/or wings